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Effect of time of removal of annual grasses from pastures on the carryover of take-all to wheat

C.R. Kid, A.R. Leys, J.E. Pratley and G.M. Murray

NSW Agriculture, Agricultural Research Institute, Wagga NSW 2650
Charles Sturt University-Riverina, Wagga NSW 2650

Take-all disease, caused by the fungus Gaeumannomyces graminis var. tritici (Ggt), is one of the most damaging diseases of Australian wheat. A wide range of pasture grasses host the fungus as well as wheat and barley. Thus, it can be carried through the pasture phase into a succeeding cereal crop on the infected residues of these grasses. Herbicides can remove grasses from pastures in the year before cropping and eliminate the carryover hosts. The effectiveness of grass control in reducing the incidence of take-all depends on herbicide efficacy and time of application. Consequently, a series of field experiments was established in southern NSW to quantify the effect of time of removal of annual grasses on the incidence of take-all disease in following wheat crops.


Five sites were selected to cover a range of environments (average annual rainfall and soil type) and pastures. Herbicides were used to remove grasses, vulpia (Vulpia myuros and V. bromoides), and great brome (Bromus diandrus), from pastures at various times from early June to late October during the 1990 season. In May/June of 1991 these sites were planted to wheat and Ggt allowed to develop. Data on disease incidence and crop yield will be examined to determine the effect of grass removal and environment on take-all.

Results and discussion

Ggt had colonised roots of wheat plants at all sites by July 1991. Initial indications are that there is less infection in treatments where grasses were removed from the pasture early in 1990. However, survival of Ggt is affected by the rate of breakdown of infested plant residues in the soil by micro-organisms. Dry conditions frequently inhibit this breakdown during summer in southern Australia (1). Traditional methods of grass/disease control such as fallow commencement in August or September, or spraytopping in October, are likely to be less effective, especially if little or no rain falls in spring and summer. Thus, to allow adequate time for microbial activity under moist conditions, grasses must be removed during winter.


We thank Dr P.T.W. Wong for confirmation of Ggt. This research is funded by the Land and Water Resources Research and Development Corporation.


Cotterill, P.J. and Sivasithamparam, K. 1987. Plant and Soil 103, 289-91.

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